how to insert a delimiter into an array powershell

#Group Users expression adds semicolon using the join command
   #Dewilrig Expression / Value pair that defines group and objects that will be mapped to specific column values within Excel output
   #Pipe output exported to .csv with date timestamp 
   $ExtSiteGroup1 | Select-Object @{name="Site Title";Expression={[String]$Site.Title}},@{name="Site URL";Expression={[String]$Site.URL}},
   @{name="Site Sharing Capability";Expression={[String]$Site.SharingCapability}},@{name="Group Name";Expression={[String]$_.Title}},@{Name=’Group Users’;Expression={[String]::join(“;”, ($_.Users))}},
   @{name="Groups or Group Role";Expression={[String]$_.Roles}} | Export-Csv C:\Data\ExtUserReport-$Date.csv -NoTypeInformation -Append

}